Download a spectrum emulator first, and install it on your PC. The one you choose will be dependant on your operating system and whether you want to pay for one or not (many are free). Also, there are various formats of ROMs and other files that the emulators can handle, so it may be worth researching which format has the most games you want.
http://www.worldofspectrum.org/ has a good overview, though I'm not sure how up to date it is (it does have links to the game you mention though).
http://www.cryptacet.com/spectrum/step1.cs4 has a step-by-step (but out of date) tutorial on what to do - you may want to use different software, though.
I've never got around to using a Speccy emulator, so I can't personally recommend one, I'm afraid.